The invention relates to a material for a hole transport layer with a p-doping agent.
It is known that the efficiency, for example expressed in cd/A or Im/W, and the lifetime (in hours) of organic light emitting diodes can be increased by introducing special layers for electron or hole transport. Since the layers are processed from solution, the solubility of the materials in particular is a basic prerequisite for their applicability.
Hole transport layers for polymer-based organic light emitting diodes are mostly produced from an aqueous solution of poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid (PEDOT:PSS).
It has however become evident that this material has disadvantages. Firstly, the highly acidic sulfonic acid it contains etches the electrode layer lying beneath which as a general rule is formed of ITO (indium tin oxide), and secondly it is known that the boundary surface between the light-emitting layer and the hole transport layer formed of PEDOT:PSS has too short a service life for economic applications.